Field of the Disclosure
The present disclosure generally relates to rechargeable implantable electrical devices. More particularly, the present disclosure relates to an implantable device, with an inductive recharging system, having a metal case that is designed to reduce the effects of eddy currents during recharging.
Description of the Related Art
There are a variety of implantable devices for which it is desirable to provide inductive electrical recharging. Such devices can include pacemakers, implantable drug delivery systems and nerve stimulation devices. Among the latter are implantable devices for nerve stimulation, such as vagus nerve stimulation (VNS). VNS has been used as a treatment for intractable epilepsy. VNS is achieved through an implanted device, such as a pulse generator that delivers a bipolar, biphasic pulse to the vagus nerve. The implant procedure is very similar to the implantation of a pacemaker. The pulse generator is implanted subcutaneously, typically in the upper left chest wall. An electric lead is connected between the pulse generator and one or more electrodes on the vagus nerve using a subcutaneous tunneling tool to the left vagus nerve, which lies in the carotid sheath.
Many implantable devices were originally designed with non-rechargeable batteries. More recently, however, rechargeable devices have been developed, allowing a user to periodically recharge the device using an inductive recharger that is magnetically coupled with inductive recharging elements of the implanted device. Such recharging presents several challenges. In many implantable devices, the inductive recharging elements of the implanted device are located in the body of the device itself, which is often housed in a metal case, made of materials such as stainless steel or titanium. Unfortunately, the metal case can contribute to the formation of eddy currents during inductive recharging. These eddy currents waste energy (which lengthens the time required for recharging) and also cause heating of surrounding tissue, which is a significant issue.
It is desirable to provide safe, simple, and convenient recharging of implanted devices, while minimizing the production of eddy currents and undesirable heating of surrounding tissues. The present disclosure is directed to overcoming, or at least reducing the effects, of one or more of the issues set forth above.